@Law:
she is a zoan if she could turn into wind/air then she would be a logia.
Marco can turns into a bird which consist of a magic blue fire, but he is not a logia, he is a mystic zoan. She can turn herself into something which consist of magic transparent wind. Legend says than Phoenix is a bird of regenerating fire, but about harpies it says that they a personification of storm winds and sometimes that they can turns into wind.
@Strelok:
Why do you think harpies can become magic wind? :ninja:
It's one of the abilities that they have according to some myths.